Antacid composition



Jan. 16, 1962 Filed April 6. 1959 s. M. BEEKMAN 3,017,324

ANTACID COMPOSITION 5 Sheets-Sheet 1 CODE 0 Q WEE.

TIME

FIG.

INVENTOR;

STEWART M. BEEKMAN 8 Maui-M ATTORNEYS Jan. 16, 1962 s, BEEKMAN 3,017,324

ANTACID COMPOSITION Filed April 6, 1959 5 Sheets-Sheet 2 EXAMPLE No. RATO 3 use FIG. 2.

INVEN TOR. STEWART M. BEEKMAN BY W'MM*M A T TORNE Y5 Jan. 16, 1962 FiledApril 6, 1959 s. M. BEEKMAN 3,017,324

O 20 4O 6O 80 I00 I20 TIME FIG. 3.

IN VEN TOR.

STEWART M. BEEKMAN BY 51. Mkimu A TTORNE Y5 Jan. 16, 1962 s. M. BEEKMAN3,017,

ANTACID COMPOSITION Filed April 6, 1959 5 Sheets-Sheet 4 CODE Al O =MqOg mm m A 82 0 2o 40 so 80 I00 I20 TIME INVENTOR. STEWART M. BEEKMANATTORNEYS Jan. 16, 1962 s. M. BEEKMAN 3,017,324

ANTACID COMPOSITION Filed April 6, 1959 5 Sheets-Sheet 5 CODE Al O =MqOEXAMPLE No. w

0 2o 40 so 80 I00 I20 TIME FIGI 5o INVENTOR.

STEWART M. BEEKMAN BY QM ATTORNEYS lnited States Patent 3,017,324ANTACID COMPOSITION wart M. Beekman, Berkeley Heights, N.J., assignor toieheis Company, Inc., a corporation of New York Filed Apr. 6, 1959, Ser.No. 804,414 Claims. (Cl. 167-55) [his invention relates to an antacidcomposition, and re particularly to an antacid composition comprisingminum hydroxy carbonate and magnesium silicate, and a process ofpreparing the same. Antacid preparations are now quite generallyemployed the treatment of peptic ulcers, gastric hyperacidity andspepsia. Gwilt, Livingstone and Robertson in the Jouri of Pharmacy andPharmacology, X, No. 12, 770-775 958), describe the characteristics ofan ideal antacid. iey point out that it should show its maximumneurlizing effect in the shortest possible time, that it should utralizean adequate amount of gastric hydrochloric id and maintain its actionduring the normal period of vstric digestion, that any excess howevergreat beyond e amount required to neutralize free gastric acid should atcause alkalization, that it should raise the pH of the istric contentsto a :level at which pepsin activity is relced significantly but nottotally inhibited, that adequate 1d repeated doses should be palatableto the hyperacid itient, and that its use should not lead to laxative,conipating or other side effects such as gastric irritation. In lditionto these factors the antacid composition should 2 inexpensive and itshould not deteriorate significantly l any respect on aging. Theseworkers summarize the arious statements in the literature as to the pHranges esirable for the ideal antacid, and conclude that a pH within therange from about 3.5 toabout 4.5 is apparntly the optimum to ensureadequate relief from hyperctidity, particularly if an ulcer site ispresent, and at the ame time permits sufficient residual pepsin activityto .void secondary digestive disturbances.

Edwards in The Chemist and Druggist, December 14, .957, page 647, alsodiscusses the properties of an ideal intacid, and suggests that thenearest approach to the deal attained as of that date was wet activatedalumina gel. Dr. Edwards views ot the proper-ties of the ideal antacidare in substantial agreement with those expressed 9y Gwilt et al.

Liquid aluminum hydroxide gel closely approaches the ideal for anantacid but its liquid form makes it inconvenient to use, especially inthe case of ambulatory patients. The liquid gel is quite rapid in itsaction and gives a prolonged antacid effect in the optimum pH range. Itis not significantly affected in its antacid properties by pepsin and italso does not significantly lose its antacid characteristics in aging.However, as Edwards and others have pointed out, it may have a mildlyconstipating effect which many have sought to remedy by combining itwith other ingredients such as magnesium hydroxide or carbonate.

The advantages of the dried gel are obvious. However, the obviousmaterial, dried aluminum hydroxide gel, is actually far from an idealantacid. It exhibits a lag in its rate of reaction with stomach acids.It does not give a prolonged antacid in the optimum pH range and itsantacid properties are severely affected by pepsin. Also, its antacidactivity is less than that of the liquid ice igel, being decreased bythe drying and the reduced activity decreases further with aging. Thesedisadvantages have been noted by Gwilt et a1. and other workers in thisfield.

German Patent No. 941,864 describes an antacid composition composed ofmixed coprecipitated aluminum and magnesium hydroxy silicates preparedfrom sodium silicate and sodium hydroxide by reaction with magnesiumsulfate and aluminum sulfate. The product is described as having theformula AlMg Si O This preparation is shown by the patent graph to besuperior to sodium bicarbonate, calcium carbonate, magnesium carbonateand magnesium trisilicate. However, according to the test used, the pHshortly following its administration rises to 6 or above, and remainsabove 4.5 for approximately minutes, which is too high for asatisfactory antacid preparation.

In accordance with the instant invention, there. is provided an antacidcomposition composed of a mixture of magnesium silicate and aluminumhydroxy carbonate in certain proportions. This composition is capable ofmaintaining a pH in the stomach within the range from 3 to 4.5 for twohours or longer, and is thus characterized by a remarkably constant pHin the optimum range for a sufliciently long time per dose to enable thepatient to avoid irritation with a minimum of medication.

The proportions of aluminum hydroxy carbonate and magnesium silicate arequite critical in maintaining a fast antacid action within this pHrange. The molecular ratio Al O :MgO of aluminum hydroxy carbonatecalculated as A1 0 to magnesium silicate calculated as MgO should bewithin the range of from 1:2 to 32:2. At Al O :MgO ratios below this,the maximum pH following administration of the composition will rise toconsiderably in excess of 4.5, which is undesirable. Proportions of A1 0in excess of 32:2 can be used without disadvantageously affecting pH,but with the detriment that the composition is greatly slowed in itsantacidaction, so that the desired pH is not reached until aconsiderable time following administration, which also is undesirable.Thus, the stated range represents the optimum proportions of theessential ingredients for effective and prompt antacid action.

The composition can be prepared in any of several ways. The onlyprerequisite is that the aluminum hydroxy carbonate be in hydrousgelatinous form at the time of mixing with the magnesium silicate. Thealuminum hydroxy carbonate must not have been dried prior to use, thatis, it must be in moist, undried form. It must contain at leastsuflicient of the original gel water to make it moist. There are severalmagnesium silicates, with varying MgOzSiO ratios, but the trisilicate2MgO:3SiO .,,H O is preferred The magnesium silicate can be in the formof a dry gel which is physically mixed with the moist aluminum hydroxycarbonate. It is usually more desirable, however, to blend the magnesiumsilicate in freshly precipitated moist gel form with the aluminumhydroxy carbonate, since the particles are then in a more finely-dividedstate. The magnesium silicate also may be coprecipitated with thealuminum hydroxy carbonate from a common reaction solution, if desired,containing silicate, hydroxyl,

carbonate, magnesium and aluminum ions, such as a mixture of sodiumsilicate, sodium carbonate, sodium hydroxide, magnesium sulfate andaluminum sulfate, in

proper stoichiometric proportions to give the desired precipitate. Thisprocedure is somewhat more complicated, requiring more careful controlof the precipitation conditions so as to obtain a good precipitate ofboth these salts, in the desired proportions, and therefore is lessdesirable than the others.

The resulting mixture prepared as above described is dried by anyconvenient method known to those skilled in the art, such as forexample, spray or tray drying. The final composition is in the form of adried gel which can be reduced to powdered form for convenience ofpackaging and marketing.

The following examples in the opinion of the inventor represent the bestembodiments of his invention.

EXAMPLE 1 370 lbs. of precipitated magnesium trisilicate slurry (0.895%MgO, 2% SiO;, pH 9.7) was blended with 525 lbs. of freshly precipitatedbasic aluminum hydroxy carbonate slurry (1.6% A1 pH 5.3) in a 150 gallonHaveg cylindrical tank using a H.P. 425 r.p.m. portable type agitatoremploying two inch marine type propellers. After fifteen minutes ofagitation the pH of the blend was measured and found to be 7.35.Agitation was continued for a total of one hour.

The resulting slurry, which had an alumina content of 0.939%, wasfiltered through a 12 inch Shriver filter press equipped with plasticplates and frames. Three cycles were required for filtering and washingthe entire batch.

Each cycle required eighty minutes at 45 p.s.i.g. and eight 30 hourswashing time. The white filter press cakes obtained had a total weightof 116.31 lbs.

The cakes were dried in a circulating air dryer in the pilot plant at125 F. yielding 20.06 lbs. of dry product. The dried lumps werepulverized in a No. 1 Mikro pulverizer at 9600 r.p.m. using an 0.020inch herringbone screen. The product analyzed as follows:

Al O :MgO ratio 2:2 A1 0 percent 28.6 MgO do 115 SiO- do 25.3 CO2 d0Moisture (Dean & Starke) do 13.6 Sulfates (S0 do 0.03 Chlorides (Cl) do0.03 1 pH (4% aqueous dispersed) 9.8 Apparent density (g./ml.) 0.16Screen analysis:

Percent through 200 mesh 95.2

Percent through 325 mesh 83.3 Acid consuming capacity (ml. N/ HCl/g.)205 The antacid characteristics were determined by the method ofHolbert, Noble and Grote, Journal of the American PharmaceuticalAssociation, 36, 149 (1947), 37, 292 (1948), Murphey, 0d, a test sampleof antacid is added to 150 ml. of pH 1.5 hydrochloric acid containing 2g. of pepsin N.F. per liter (artificial gastric juice) at 37.5 C. ml. ofthe artificial gastric juice is withdrawn every ten minutes and replacedwith an equal volume of fresh gastric juice. The test procedure used inthe work reported in this and the following examples, however, wascarried out by continuously introducing fresh artificial gastric juiceand removing the antacid-gastric juice mixture by overflow at the rateof 2 ml. per minute. Theantacid effect is determined by measuring the pHof the artificial gastric juice during the test period, which was twohours 120 minutes).

The pH data taken in this test, carried out on a 1 gram sample, arereported below in Table I.

41, 361 (1952). In this methnate gel (303 g. A1 0 4 Table I ANTACIDCHARACTERISTICS The data show that the composition was capablemaintaining the pH within the range from 3.2 to 4 f two hours.

EXAMPLES 2 TO 6 A group of five compositions was prepared by intimat lyblending moist basic aluminum hydroxy carbonate g with aqueousgelatinous magnesium trisilicate, follows by drying and reduction topowder. The proportions aluminum hydroxy carbonate as A1 0 to magnesiumtr silicate as MgO ranged from 8:2 to 1:4 (0.5:2).

The magnesium trisilicate gel employed in the:

35 preparations was prepared from magnesium sulfal MgSO -7H O and sodiumsilicate Na SiO (40 Baumr 9.13% Na O, 28.2% SiO 262.5 lbs. of magnesiursulfate was dissolved in 232 lbs. of water. 4.935 lbs. 0 sodiumhydroxide was dissolved in 20 lbs. of water, anl these were mixed in37.25 lbs. of the sodium silicat solution, and 200 lbs. of water thenadded. The solu tions were mixed in a Haveg reactor with a marine typipropeller. The solution was allowed to age for one hou: after mixing hadbeen completed, and the magnesium tri silicate separated by filtration;44.5 lbs. of cake was ob tained.

(Example 2) was prepared from a blend of 5000 g. moist aluminum hydroxycarbonate gel g. A1 0 and 1210 g. of magnesium tri- 0 silicate gel (49.7g. MgO). 2000 g. of deionized water was placed in a three gallon mixingtank, and the aluminum hydroxycarbonate was thoroughly dispersed thereinusing a 0.5 H.P. laboratory Dispersator. The magnesium trisilicate gelwas added, and the slurry intimately blended at high speed for fiveminutes. The wet gel contained 5.79% A1 0 and 0.57% MgO. The particleswere spread out on a tray and dried in an atmospheric tray dryer at F.for nine hours. The mixture was pulverized to a fine powder by one passthrough a No. 1 Mikro Pulverizer at 5000 r.p.m. using a 0.020 inchherringbone screen.

The 2:2 product (Example 4) was prepared by the same procedure, using3000 g. aluminum hydroxy carboand 2840 g. magnesium trisilicate gel(119.4 g. MgO). 1500 g. of water was used. The wet gel contained 4.13%A1 0 and 1.62% MgO.

The 1:2 product (Example 5) was prepared from 2000 g. aluminum hydroxycarbonate gel (202 g. A1 0 and 75 3790 g. magnesium trisilicate gel(159.5 g. MgO). 1000 g.

pared by hydroxy carbonate gel icate gel of. deionized water to testedfor antacid activity Noble, and Grote test prole 7) was pre gh to blend.Agitation was Mole Ratio lailuminum A1 0 and 1.91 lbs. magnesium trisil500 ml. fluid enou Apparent Density,

The gels were using the modified Holbert, cedure.

g0) with 2 the mixture followed by drying at 150 F. and pulverizing topow- The 12:2 product (Examp adding 12 lbs. of 10.1

Screen Test, Percent Remaining dered form.

5 and additional (4.21% M render Carbonates as CO2,

Table II t percent carbonate gel (126.25 trisilicate (199 g. MgO) Acid 1Consuming Cl Capacity percen droxy lyzed as follows:

Si O 2 duct (Example 6) was prepared blended at high speed d. The wetgel containe MgO, percent percent A12 percent later was used. The wetgel contained 2.97

2.35 MgO. he 0.5:2 (1:4) pro n 1250 g. aluminum by .1 0 and 4730 g.magnesium two gels were cr was not require 0, and 3.33% MgO. The driedproducts ana ample No.

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is the pH of the original gastric 5) represents the minimum desirableproportion of alu- The above data are EXAMPLES 7 To 9 70 It is apparentthat eac ble of maintaining a p approximately For purposes ofcomparison, dried gel U.S.P. having a pH of pletely unsatisfactory.

EXAMPLES 10 TO 13 A group of antacid preparations were prepared byblending dried magnesium trisilicate U.S.P. with wet aluminum hydroxycarbonate gel in the Al O :MgO molecular ratios of 8:2, 4:2, 2:2 and1:2, drying the mixtures in air at 150 F., pulverizing them to -apowder, and then determining the antacid characteristics using the invitro test method of Holbert, Noble and Grote as set forth in Example 1.The magnesium trisilicate used contained 22% MgO, and the aluminumhydroxy carbona-te gel contained 10.1% A1 and 4.3% carbonates 3S In eachcase, 50 g. of magnesium trisilicate powder was thoroughly mixed andblended with the aluminum hydroxy carbonate gel. 1100 g. of the gel wasused to make the 8:2 product (Example 10), 550 g. for the 4:2 product(Example 11), 775 g. for the 2:2 product (Example 12) and 137 g. for the1:2 product (Example 13). 250 ml. of deionized Water was added to makethe blend more fluid and to facilitate mixing. The mixtures were driedin an air circulating dryer at 140 F. until constant weight was reached,and the dried samples were finely pulverized in a Mikro pulverizedsample mill.

The pH data obtained using 1 .gram samples by the Holbert, Noble andGrote test procedure are set forth in the table below.

Table V Example N0. M 10 11 12 13 The above data are Each of thesecompositions is capable of maintaingraphed in FIGURE 3.

ing the pH Within the two hours.

These results are to be contrasted with the results obtained when adried aluminum hydroxide gel U.S.P. is mixed with the dried magnesiumtrisilicate U.S.P. to form a simple dry blend. Such blends were preparedusing magnesium trisilicate U.S.P. (22% MgO) and dried aluminumhydroxide gel U.S.P. (53.7% A1 0 8:2 (blend A), 4:2 (blend B), 2:2(blend C), 1:2 (blend D) and 0.5 :2 (1:4) (blend E) products wereprepared using 9.32 g. dried aluminum hydroxy gel to furnish 5 g. A1 0and 2.24 g., 4.50 g., 9 g., 17.95 g. and 35.95 g. magnesium trisilicateto furnish 0.494, 0.989, 1.975, 3.95 and 7.91 'g. MgO, respectively. The

range of 3 to 4.2 for approximately 8 blends were then tested by theHolibert, Noble Grote procedure as outlined in Example 1, using gramsamples. The pH data obtained was as follows Table VI N Blend BlendBlend Blend Ble A B O D E 1. 5 l. 5 l. 5 1. 5 2. 0 2. O 2. O 2. O 2. 02. 0 2. 01 2. 04 i 2. 0 2. 0 2. 05 2. 13 2 2. 0 2. 00 2. 11 2. 22 2 2. 02. 02 2. l9 2. 34 2 2. O 2. O4 2. 25 2. 48 2 2. 05 2. 21 2. 60 3. 22 42. 12 2. 38 2. 99 3. 78 5 2. 12 2. 42 2. 3. 66 4 2. 08 2. 3S 2. 67 3. 204 2. 02 2. 30 2. 49 2. 88 3. 2. 02 2. 23 2. 35 2. 61 3. 2. 0 2. 16 2. 252. 45 2. 2. 0 2. 11 2. 17 2. 32 2. 2. 0 2. 08 2. 11 2. 21 2. 2. 0 2. 062. 08 2. l7 2. 2. 0 2. 02 2. O5 2. l0 2. 2. 0 2 00 2. 03 2. 06 2.

These data are graphed in FIGURE 4.

It is apparent from the above data that these compos tions are incapableof meeting the requirements for satisfactory antacid composition. BlendsA to C di not even reach a pH of 3. Blend D maintained a pl above 3 onlyfor thirty minutes and blend E maintaine this pH for only fifty minutes,while the maximum pl reached 5.2 well beyond the desirable upper limitof 4.5 Thus, the data show the significance of mixing the mag nesiumtrisilicate with a wet aluminum hydroxy carbonan gel.

EXAMPLES 14 TO 16 Three compositions were prepared having Al O :MgCmolecular ratios of 8:2, 2:2 and 1:4. These compositions were preparedfrom aluminum sulfate and magnesium sulfate by reaction thereof inalkaline aqueous sodium silicate solution, followed by coprecipitationof the two substances.

The magnesium sulfate and aluminum sulfate were both dissolved indeionized water in a tank equipped With a Lightnin' portable agitatorwith a 2 inch at blade turbine. The sodium silicate (40 Baum 28.2% SiOand caustic soda pellets were dissolved separately in deionized waterand the magnesium silicate-aluminum hydroxide gels coprecipitated by theaddition of the sodium silicate solution to the mixed sulfate solutionat about 26 ml. per minute at room temperature. The precipitated slurrywas aged for sixteen hours and filtered through a 24 cm. Buchner funnelunder 23 inches of vacuum. The filtered cake was washed with deionizedwater until the effluent was sulfate-free. The wet cake was dried fortwenty-four hours at 176 F. in an atmospheric tray dryer and the driedmaterial pulverized in a Mikro sample mill.

The 8:2 composition (Example 14) was prepared from 60.4 g. MgSO -7H Oand 580 g. aluminum sulfate ironfree dissolved in 6500 ml. of deionizedwater, using as the precipitant 79 g. of the sodium silicate and 246 g.caustic soda pellets dissolved in 5868 g. of deionized water.

The 2:2 product was prepared from 121 g. MgSO -7H 0 in 580 g. ofaluminum sulfate, iron-free, added to 6499.6 g. deionized water, using316 g. sodium silicate and 278 g. sodium hydroxide pellets dissolved in5602 g. deionized water.

The 1:4 product (Example 16) was prepared from 134 g. of magnesiumsulfate and 79.0 g. of aluminum sulfate, iron-free, dissolved in 770 g.of deionized water, using as precipitant 170.5 g. of sodium silicate and56 g. caustic da dissolved in 631 g. deionized water.

The antacid characteristics of these three materials were .termined bythe Holbert, Noble and Grote procedure .ing 1 gram samples as set forthin Example 1 above. he pH data obtained was as follows:

Table VII Example 14 Example 15 Example 16 A120 hlgO A110 MgO Al O zNlgoRatio, 8:? Ratio, 2:2 Ratio, 0.33:2

1. 5 l. 5 l. 5 2. 3. 8 3. 2 2. 3 3. 9 3. 6 3.0 3. 9 3. S 3. 6 4. 0 4.33. 7 4. 0 4. 6 3. 7 4. 0 4. 8 3. 7 4.0 5. 0 7 4. 0 5.1 3. 7 4.0 5. 2 3.7 4. 0 5. 2 3. 7 4. 0 5. 3 3. 8 4.0 5. 3 3. 7 4. O 4. 6 3. 6 3. 9 4. 33. 3. 8 3. 9 3. 1 3.7 3. 6 3. 3 3. 7 3. 5 3. 2 3.6 3.3 3.0 3. 5 3. 2 2.9 3. 4 3. 0 2. S 3. 2 2. 9 2. 6 3.1 2. 7 2. 5 2. 8 2. 6

These data are graphed in FIGURE 5.

These data show the criticality of the Al O :MgO ratio. Examples 14 and15 are capable of maintaining the pH within the range from 3 to 4.5 forapproximately two hours. The Example 16 composition with a 1:4

ratio could not maintain an upper pH limit at 4.5 or below. The pH wasin excess of 4.5 for most of the first twenty minutes of the testprocedure, which is undesirable. Thus, in this composition there was toolittle aluminum hydroxide.

As previously indicated, the compositions in accordance with theinvention are useful in the treatment of internal conditions whereexcess acidity is to be encountered, such as gastric acidity in thestomach, in, for example, the treatment of gastric and peptic ulcers.For this purpose, the dry compositions are readily administered in theform of slurries, or as dry powders or tablets, with an excipient, ifdesired, which are suitably taken orally or added to a liquid carriersuch as water.

It is usually most convenient to prepare the compositions in tabletform, and since the compositions are relatively inert and store well,tablets are easily prepared by conventional procedures. The compositioncan be tableted as such, or with an excipient mixture of conventionalThe quantity indicated is sufficient to prepare approximately 48,000tablets, containing 10 grains each of the antacid composition.

Those skilled in the art will perceive other methods for theadministration of the compositions, and it will be apparent that theseare in no way critical but can be selected to meet any particularrequirements.

I claim:

1. An antacid composition capable as determined by the Holbert, Nobleand Grote test method of maintaining the pH of artificial gastric juicewithin the range from about 3 to about 4.5 for at least one hour,comprising the dried combination of hydrous gelatinous aluminum hydroxycarbonate and magnesium silicate, in a molecular weight ratio calculatedas Al O :MgO within the range from about 1:2 to about 32:2.

2. An antacid composition in accordance with claim 1 in which themagnesium silicate is in the form of dry magnesium trisilicate gel.

3. An antacid composition in accordance with claim 1 in which themagnesium silicate is in the form of moist magnesium trisilicate gel.

4. A composition in accordance with claim 1 in which the aluminumhydroxy carbonate and the magnesium silicate are in the form ofcoprecipitated gels.

5. A composition in accordance with claim 1 in the form of a slurry ofthe gels in water.

6. An antacid tablet comprising a composition in accordance with claim 1and an excipient.

7.. A process for preparing an antacid composition capable as determinedby the Holbert, Noble and Grote test method of maintaining the pH ofartificial gastric juice within the range from 3 to about 4.5 for atleast one hour, which comprises mixing hydrous gelatinous aluminumhydroxy carbonate and magnesium silicate in a molecular weight ratiocalculated as Al o zMgO within the range from about 1:2 to about 32:2,and drying the resulting mixture.

8. A process in accordance with claim 7 in which the aluminum hydroxycarbonate gel and magnesium silicate are formed in situ bycoprecipitation from a common solution.

9. A process in accordance with claim 7 in which the magnesium silicateis a dry magnesium trisilicate gel.

10. A process in accordance with claim 7 in which the magnesium silicateis a moist magnesium trisilicate.

2,797,978 Beekman July 2, 1957 corrected below.

UNITED STATES- PATENT. OFFICE I CERTIFICATE 0F CORRECTION Patent No.3,017,324 January 16 1962 Stewart M. Beekman above numbered patcertifiedthat error appears in the should read as It is hereby tion and that thesaid Letters Patent ent requiring correc Column 5, line 41, Table 111,Example N0. 6, and opposite "1.0" for 2.9" read 4.0

d and sealed this 15th day of May 1962.

Signe (SEAL) Attest; h I

ERNEST W. SWIDER "DAVID LA-DD Attesting Officer Commissioner of Patents

1. AN ANTACID COMPOSITION CAPABLE AS DETERMINED BY THE HOLBERT, NOBLE AND GROTE TEST METHOD OF MAINTAINING THE PH OF ARTIFICIAL GASTRIC JUICE WITHIN THE RANGE FROM ABOUT 3 TO ABOUT 4.5 FOR AT LEAST ONE HOUR, COMPRISING THE DRIED COMBINATION OF HYDROUS GELATINOUS ALUMINUM HYDROXY CARBONATE AND MAGNESIUM SILICATE, IN A MOLECULAR WEIGHT RATIO CALCULATED AS AL2O3:MGO WITHIN THE RANGE FROM ABOUT 1:2 TO ABOUT 32:2. 